fascinating. Apparently nearly identical sets or maybe the same set sold by different companies. Or perhaps one sold the others set?
The article from the poster stamp bulletin October 1944
http://www.alphabetilately.org/Cisfor/PSB/09-5-1.html
And their ad from later in the same issue.
http://www.alphabetilately.org/Cisfor/PSB/09-5-6.html
A bit confusing since they describe it as a set of 30 in one part of the article but later call it a set of 24 and show it as 24 in the ad.
As near as I can tell, they're the same set.
Steve B